1. Field of the Invention
The invention relates in general to sewing machines and in particular to a new and useful sewing machine with a feed roller, a spring-loaded carrier carrying the feed roller and moving substantially in vertical directions, a driving wheel; arranged, with respect to the sewing direction, behind the feed roller, and which is in operating connection with a drive shaft, and a belt running over guide rollers which forms the driving connection between the feed roller and the driving wheel.
2. Description of the Prior Art
The known sewing machines have a disadvantage that the vertical component of the driving force acting on the pulling strand of the drive belt has a disadvantageous effect on the pressure of the feed roller on the sewing material while pressure is necessary for a satisfactory feed of the sewing material. This has a particularly unfavorable effect when a pulling force is required for feeding the sewing material, for example, when sewing over transitions or when using cloth guiding apparatus which offer a different resistance to the sewing material at different thicknesses. The variable belt force necessary for carrying out these operations influences the pressure of the feed roller on the sewing material, particularly when it is necessary to maintain the normal pressure for a satisfactory feed of the sewing material. When the pressure of the feed roller varies with changing driving requirements, the uniformity of the feeding action of this roller is impaired, and thus also the sewing result.
The invention provides a belt drive where the pressure of the feed roller remains constant with changing driving forces. In accordance with the invention, the guide roller for the pulling strand of the belt is rotatably secured on a rocker pivotally mounted coaxially to the driving wheel.
The part of the strand extending between the guide roller and the driving wheel is substantially horizontal, and the rocker is connected with a carrier for the feed roller over a coupling rod whose longitudinal axis intersects the bisector of the looping angle of the belt about the guide roller substantially in the horizontal plane through the axis of rotation of the rocker.
Accordingly, it is an object of the invention to provide a sewing machine for sewing and feeding material which has a housing with a main shaft rotatable in the housing for driving the needle, and with a feed roller carrier which is mounted on a pressure rod which depends from the housing for movement upwardly and downwardly, which carries a feed roller which is rotatable thereon which engages the material to be fed, and wherein a feed roller carries a driven gear which is driven from a drive gear through a drive belt, and wherein the drive gear is intermittently driven from the main shaft, further including a connecting rod connected between the carrier and a rocker which is pivoted on the same axis as the drive gear, and which carries two guide rollers over which the drive belt is driven, and wherein the connection between the connecting rod and the rocker is such that the belt forms an engagement angle about one of the guide rollers which has a bisector which intersects the longitudinal axis of the connecting rod substantially in the horizontal plane extending through the axis of rotation of the rocker.
A further object of the invention is to provide a sewing machine which has a drive roller which is mounted to engage the material being threaded which is connected to a drive mechanism such that there is substantially no lifting force produced by the pull of the drive belt which drives the drive roller during the feeding of the material.
A further object of the invention is to provide a sewing machine which is simple in design, rugged in construction, and economical to manufacture.
The various features of novelty which characterize the invention are pointed out with particularly in the claims annexed to and forming a part of this disclosure. For a better understanding of the invention, its operating advantages and specific objects attained by its uses. Reference is made to the accompanying drawings and descriptive matter in which preferred embodiments of the invention are illustrated.